This invention relates to vacuum cleaners which are suitable for picking up particles which are normally too large to be picked up by conventional vacuum cleaners. The particles may be composed of, for example, excrement of animals and birds, pine cones, twigs and pieces of bark. More particularly the invention relates to vacuum cleaners having conical filters for use in picking up relatively large particles such as those mentioned above.
Vacuum cleaners are known which have conical filters. Such filters have the advantage over flat filters in that they have a larger effective filtering surface for a given area through which air to be filtered passes. Examples of such vacuum cleaners are described in such U.S. patents as no. 2,719,596 to Kent et al.; U.S. Pat. No. 3,910,781 to Bryant; U.S. Pat. No. 5,287,591 to Rench et al.; U.S. Pat. No. 5,305,495 to Nelsen et al.; U.S. Pat. No. 5,307,538 to Rench et al.; and U.S. Pat. No. 5,593,479 to Frey et al.
Vacuum cleaners such as those referred to above are suitable for picking up relatively small particles such as dust and dirt but have limited or no usefulness where the particles are larger. Larger particles quickly clog the machines and render them useless after a short period of time. In addition vacuum cleaners typically have cloth or paper bags in which the particles are collected. Such bags are not suitable for larger particles because they tend to rip or to become clogged by such particles. In addition they burn if the vacuum cleaner picks up cigarette or cigar butts that are still burning.